This article scrutinizes the assumption that friends support each other in times of war. Picking up the notion that solidarity, or 'other-help', is a key feature of friendship between states, the article explores how states behave when a friend is attacked by an overwhelming enemy. It directs attention to the trade-off between solidarity and self-help that governments face in such a situation and makes the novel argument that the decision about whether and how to support the friend is significantly influenced by assessments of the distribution of material capabilities and the relationship the state has with the aggressor. This proposition is supported empirically in an examination of Sweden's response to its Nordic friends' need for help during the Second World War - to Finland during the 1939-1940 'Winter War' with the Soviet Union, and to Norway following the invasion of Germany from 1940 to 1945.